https://github.com/andrey-ushakov/esc_pos_utils/pull/110

Author: Denis Rudnei de Souza

lib/src/generator.dart

@@ -8,11 +8,12 @@
 
 import 'dart:convert';
 import 'dart:typed_data' show Uint8List;
+
+import 'package:esc_pos_utils/esc_pos_utils.dart';
+import 'package:gbk_codec/gbk_codec.dart';
 import 'package:hex/hex.dart';
 import 'package:image/image.dart';
-import 'package:gbk_codec/gbk_codec.dart';
-import 'package:esc_pos_utils/esc_pos_utils.dart';
-import 'enums.dart';
+
 import 'commands.dart';
 
 class Generator {
@@ -69,10 +70,9 @@ class Generator {
     // replace some non-ascii characters
     text = text
         .replaceAll("’", "'")
-        .replaceAll("‘", "'")
         .replaceAll("´", "'")
         .replaceAll("»", '"')
-        .replaceAll(" ", ' ')
+        .replaceAll(" ", ' ')
         .replaceAll("•", '.');
     if (!isKanji) {
       return latin1.encode(text);
@@ -146,23 +146,80 @@ class Generator {
 
     // Create a black bottom layer
     final biggerImage = copyResize(image, width: widthPx, height: heightPx);
-    fill(biggerImage, 0);
+    fill(biggerImage, color: ColorRgb8(0, 0, 0));
     // Insert source image into bigger one
     drawImage(biggerImage, image, dstX: 0, dstY: 0);
 
     int left = 0;
     final List<List<int>> blobs = [];
 
     while (left < widthPx) {
-      final Image slice = copyCrop(biggerImage, left, 0, lineHeight, heightPx);
-      final Uint8List bytes = slice.getBytes(format: Format.luminance);
+      final Image slice = copyCrop(biggerImage,
+          x: left, y: 0, width: lineHeight, height: heightPx);
+      grayscale(slice);
+      final imgBinary = slice.convert(numChannels: 1);
+      final bytes = imgBinary.getBytes();
       blobs.add(bytes);
       left += lineHeight;
     }
 
     return blobs;
   }
 
+  /// Draw the image [src] onto the image [dst].
+  ///
+  /// In other words, drawImage will take an rectangular area from src of
+  /// width [src_w] and height [src_h] at position ([src_x],[src_y]) and place it
+  /// in a rectangular area of [dst] of width [dst_w] and height [dst_h] at
+  /// position ([dst_x],[dst_y]).
+  ///
+  /// If the source and destination coordinates and width and heights differ,
+  /// appropriate stretching or shrinking of the image fragment will be performed.
+  /// The coordinates refer to the upper left corner. This function can be used to
+  /// copy regions within the same image (if [dst] is the same as [src])
+  /// but if the regions overlap the results will be unpredictable.
+  Image drawImage(Image dst, Image src,
+      {int? dstX,
+      int? dstY,
+      int? dstW,
+      int? dstH,
+      int? srcX,
+      int? srcY,
+      int? srcW,
+      int? srcH,
+      bool blend = true}) {
+    dstX ??= 0;
+    dstY ??= 0;
+    srcX ??= 0;
+    srcY ??= 0;
+    srcW ??= src.width;
+    srcH ??= src.height;
+    dstW ??= (dst.width < src.width) ? dstW = dst.width : src.width;
+    dstH ??= (dst.height < src.height) ? dst.height : src.height;
+
+    if (blend) {
+      for (var y = 0; y < dstH; ++y) {
+        for (var x = 0; x < dstW; ++x) {
+          final stepX = (x * (srcW / dstW)).toInt();
+          final stepY = (y * (srcH / dstH)).toInt();
+          final srcPixel = src.getPixel(srcX + stepX, srcY + stepY);
+          drawPixel(dst, dstX + x, dstY + y, srcPixel);
+        }
+      }
+    } else {
+      for (var y = 0; y < dstH; ++y) {
+        for (var x = 0; x < dstW; ++x) {
+          final stepX = (x * (srcW / dstW)).toInt();
+          final stepY = (y * (srcH / dstH)).toInt();
+          final srcPixel = src.getPixel(srcX + stepX, srcY + stepY);
+          dst.setPixel(dstX + x, dstY + y, srcPixel);
+        }
+      }
+    }
+
+    return dst;
+  }
+
   /// Image rasterization
   List<int> _toRasterFormat(Image imgSrc) {
     final Image image = Image.from(imgSrc); // make a copy
@@ -174,7 +231,7 @@ class Generator {
 
     // R/G/B channels are same -> keep only one channel
     final List<int> oneChannelBytes = [];
-    final List<int> buffer = image.getBytes(format: Format.rgba);
+    final List<int> buffer = image.getBytes(order: ChannelOrder.rgba);
     for (int i = 0; i < buffer.length; i += 4) {
       oneChannelBytes.add(buffer[i]);
     }
@@ -578,8 +635,8 @@ class Generator {
     const bool highDensityVertical = true;
 
     invert(image);
-    flip(image, Flip.horizontal);
-    final Image imageRotated = copyRotate(image, 270);
+    flip(image, direction: FlipDirection.horizontal);
+    final Image imageRotated = copyRotate(image, angle: 270);
 
     const int lineHeight = highDensityVertical ? 3 : 1;
     final List<List<int>> blobs = _toColumnFormat(imageRotated, lineHeight * 8);